Before trying to play any instrument one should learn how to hold it – the physical aspect of the instrument. As a singer your entire body is your instrument and learning, understanding how to “hold your instrument” is the first step. Loosen up by shaking your arms and legs and gently moving your head from side to side and up and down. Raise your shoulders up and down. Relax.
The head, chest and pelvis should be supported by the spine in such a way that they align themselves one under the other – head erect, chest high, pelvis tipped so that the “tail is tucked in”.
The position of the head should allow the jaw to be free, not pulled back into the throat.. This liberates the organs in the neck. The high chest implies that the shoulders go back, but should be relaxed and comfortable.
Think of being a puppet hanging from strings, one attached to the top of you head and the other attached to the top of your breast bone. This keeps the head erect and lifts the chest , allowing the pelvis to just hang in position. Image the string pulls you a little toward the audience.
Stance one foot slightly in front of the other, don’t put your weight on your heels, not spread eagle, lean slightly forward – if you get tired, this is a good sign, using muscles that you have not used before.
Main thing is achieve a happy balance so that the parts that do the work are free, alert, yet relaxed.